Titanate and Zirconate Coupling Agents in Foamed Polymers

Abstract

Ti or Zr coupling agents chemically bridge two dissimilar species such as an inorganic filler/particulate and organic polymer via proton coordination without the need of water of condensation. They may also act as in situ catalysts in the polymer melt at >100°C independent of filler content by one or more distinct organometallic mechanisms of conventional catalysis, crosslinking, metallocene-like catalysis, repolymerization (US Patent 4,657,988), and copolymerization. For example, minor amounts of titanate in unfilled polymers will give 20% average faster polymer processing at 10% average lower temperatures while increasing mechanical properties. As a result of titanate (zirconate) coupling and catalysis – gaseous, endothermic and exothermic blowing agents are made significantly more efficient to produce lighter polymers with more uniform cell structure because at the elevated temperature where gas generation (blow) occurs polymer bubble stress (force/area) properties are maintained or increased while strain (elongation/unit length) properties are increased to as much as double or triple thus reducing open cell formation. For example, cell size variation is reduced from 6–48 micron to 9–15 micron in an exothermic azodicarbonamide-foamed PE. The density of an azodicarbonamide-foamed flexible PVC is decreased threefold from 0.408g/cc to 0.129g/cc. The amount of endothermic sodium bicarbonate needed to foam SBR (Styrene Butadiene Rubber) is reduced twenty-nine fold from 15 phr of NaHCO3 powder to 0.68 phr of a 75% active NaHCO3 paste masterbatch containing pyrophosphato titanate in the aromatic plasticizer phase.